TIVERTON, ON – April 5, 2013 – Bruce Power and the Ontario Power Authority (OPA) have reached an agreement to amend the Bruce Power Refurbishment Implementation Agreement (BPRIA) to ensure Ontario ratepayers will continue to be supplied with low-cost electricity from the Bruce B units to the end of the decade, prior to the full refurbishment of the units.
The amendment involves an extension of the floor price for the Bruce B units, which remains the lowest cost generator under contract by the OPA at 5.2 cents per kilowatt-hour. Bruce B provides 15 per cent of Ontario’s electricity demand on an annual basis."
Throughout 2013, Bruce Power will continue to invest in Bruce B with an estimated $250 million expected this year to continue to optimize the life of the units, ensuring both system reliability and price stability. Over the next five years, Bruce Power’s planned investment program in Bruce B will be approximately $1.1 billion. In addition to the base employment on the Bruce Power site, which is 4,000 people, this ongoing capital program will create approximately 500-600 temporary jobs annually in support of these investment activities.
This amendment does not change the price of the Bruce B floor nor does it impact the current arrangement in place for 3,000 megawatts of output from Bruce A. Bruce Power continues to assume all operational and investment risk related to the ongoing operation of Bruce B.

My best guess had been that Bruce Power would complete life-extension work at Bruce B similar to work done at unit 3, and currently being performed at unit 4, of Bruce A (10+ years - see this Bruce release for some details)

Clarington – Ontario Power Generation Inc. (OPG) continues to move forward with the refurbishment of the Darlington Nuclear Generating Station.
OPG has awarded an equipment supply and technical services contract to Alstom Power & Transport Canada Inc. to refurbish the four turbine generator sets at Darlington Nuclear. The contract, valued at approximately $350 million, is one of several that will be awarded for the refurbishment of the station.
“This is an important part of our refurbishment project,” said Dietmar Reiner, Senior Vice President, Nuclear Refurbishment. “We conducted thorough reviews of the major turbine and generator components, and determined that they are in good shape, with no life limiting issues. However, other factors that might affect their life need to be addressed through refurbishment. The work and upgrades associated with this contract will allow the equipment to run for another 30 years.”

Update April 6th: The Toronto Star's John Spears rightly wrote"Bruce Power is investing $1.1 billion in the units to extend their lives to between 2019 and 2020." The Bruce Power release begins:

Bruce Power and the Ontario Power Authority (OPA) have reached an agreement to amend the Bruce Power Refurbishment Implementation Agreement (BPRIA) to ensure Ontario ratepayers will continue to be supplied with low-cost electricity from the Bruce B units to the end of the decade, prior to the full refurbishment of the units.

Emphasis added.

The meaning of this is difficult to know ... but it would seem to clear up scheduling of concurrent refurbishments during the latter half of the current decade.

Added April 16th

The Ontario Power Authority has completed a contract amendment to the Bruce Power Refurbishment Implementation Agreement (BPRIA). The amendment secures a cost-effective source of electricity to the end of the decade and is the first step in a commercial agreement to secure 6,300 MW at the Bruce site for the long-term.Since 2005, Bruce Power has invested about $1 billion in its four Bruce B units and, over the next five years, plans to invest an additional $1.1 billion. These investments are extending the operational lives of the units from the original end of life dates between 2016 and 2019 to between 2019 and 2020. Bruce Power will continue to receive the floor price set out in the BPRIA, currently at 5.2 cents per kilowatt-hour, which is the lowest cost generation under contract with the OPA.This amendment provides significant financial benefit to Ontario ratepayers by securing 15 percent of Ontario’s annual electricity supply from Bruce B, which is reliable, low cost and low emission baseload power to 2020, a time period when some Bruce and Darlington nuclear units are expected to be offline for refurbishing. The OPA continues to work with nuclear operators to develop a co-ordinated schedule for the 10 remaining refurbishments to secure the output at these two sites for the long-term.